Bridge for ramps

ABSTRACT

A ramp having a bridge structure pivotally connected thereto for transferring a load onto and from the ramp and including a bridge plate having one end hinged to the ramp for selectively pivoting the bridge plate from a substantially vertical or rest position to an at least approximately horizontal or use position while tension spring means have one end connected to the ramp and the other end to the free end of a lever which is pivotable about an axis substantially parallel to the pivot axis of the bridge plate but is spaced from this last mentioned pivot axis. The free end of the lever carries a roller which engages and is adapted to roll on a cam surface of a cam connected to the bridge plate. The tension spring means varies its length when the roller moves on the cam surface during the pivoting of the bridge plate from its rest position to its use position and is shortest in its rest position.

United States Patent [191 Alten BRIDGE FOR RAMPS [76] Inventor: KurtAlten, Ringstr. 14, 3015 Wenningsen, Germany [22] Filed: Nov. 16, 1973[21] Appl. No.: 416,391

[30] Foreign Application Priority Data [451 May 20, 1975 PrimaryExaminerNile C. Byers, Jr. Attorney, Agent, or F irm-Walter Becker [5 7]ABSTRACT A ramp having a bridge structure pivotally connected theretofor transferring a load onto and from the ramp and including a bridgeplate having one end hinged to the ramp for selectively pivoting thebridge plate from a substantially vertical or rest position to an atleast approximately horizontal or use position while tension springmeans have one end connected to the ramp and the other end to the freeend of a lever which is pivotable about an axis substantially parallelto the pivot axis of the bridge plate but is spaced from this lastmentioned pivot axis. The free end of the lever carries a roller whichengages and is adapted to roll on a cam surface of a cam connected tothe bridge plate. The tension spring means varies its length when theroller moves on the cam surface during the pivoting of the bridge platefrom its rest position to its use position and is shortest in its restposition.

5 Claims, 2 Drawing Figures Nov. 20, 1972 Germany 2256802 [52] US. Cl.14/71 [51] Int. Cl. B65g 11/00 [58] Field of Search 14/71, 72

[56] References Cited UNITED STATES PATENTS 3,235,896 2/1966 Riggs 14/713,327,335 6/1967 Beckwith... 14/71 3,411,168 11/1968 l-lecker 14/713,460,175 8/1969 Beckwith 14/71 3,662,416 5/1972 Brooks 14/71 6 Ir I L II I 2 .9

BRIDGE FOR RAMPS The present invention relates to a bridge for rampswith a bridge plate which is pivotally arranged at the rear end of theramp and which is movable from its substantially vertical rest positionagainst the effect of a spring-loaded lever pivotable about a verticalaxis, into its substantially horizontal position of use while the freelever end engages the bridge plate by means of a cam disc.

Bridges of this type are known according to which the spring acting uponthe lever is a torsion spring which extends approximately over the widthof the bridge and is located within the region of the linkage area ofthe bridge plate. In view of the relatively large deviating travel whichthe torsion spring has to perform, the torsion spring has a lengthcorresponding to the widtl: of the bridge. Therefore, also the leverwhich is loaded by the effect of the torsion spring has to engage abridge rim or has to be built in at said bridge rim.

It is an object of the present invention so to design a bridge of theabove mentioned type that the mounting of the above referred to levermay be effected at any desired area of the bridge plate and maypreferably be centrally arranged so that the bridge plate may besubjected to stresses in a more favorable manner.

It is another object of the present invention to provide a bridge as setforth in the preceding paragraph in which the spring will be greatlysimplified while permitting a greater spring stroke.

These and other objects and advantages of the invention will appear moreclearly from the following specification in connection with theaccompanying drawing, in which:

FIG. 1 illustrates a bridge linked to a marginal area of a ramp andoccupying its rest position, the bridge of FIG. 1 being shown as viewedfrom below.

FIG. 2 represents a section taken along the line II-ll of FIG. 1.

The bridge for ramps according to the present invention, which isprovided with a bridge plate that is pivotally arranged at the rear endof the ramp and which is movable from its approximately vertical restposition against the effect of a spring-loaded lever pivotable about ahorizontal axis, into a substantially horizontal position of use whilethe free lever end engages the bridge plate by means of a cam path andwhile the spring acting upon the lever relaxes when pivoting the bridgeplate upwardly, is characterized primarily in that the spring actingupon the lever is a tension spring which has one end within the regionof the free lever end and has its other end within the region of thepivot axis of the bridge plate.

In this way, in comparison to the employment of torsion springs, thereis realized not only a considerable advantage in building up the bridgein view of the mounting of the spring centrally below the bridge platebut also a support of the bridge plate is possible which results inoperating forces being uniform over the entire pivot range of the bridgeplate.

Referring now to the drawing in detail, the bridge plate 1, which may bereinforced by longitudinally extending hollow beams 2, is by hinge means3 pivotally connected to the rim portion of the ramp 4. A flatiron 5which supports the hinge means 3 may be fixedly connected to the ramp 4or if desired may also be longitudinally displaceable on the ramp 4. Thedrawing shows the bridge in its vertical rest position. When the bridgeis in its operative position or position of use, the bridge plate 1rests by means of its front portion 6 on the vehicle or the like.

Centrally below the bridge plate 1 there is arranged a cam 7 which isformed by a flatiron 8 extending vertically with regard to the bridgeplate 1 and in the longitudinal direction of the latter.

The cam 7 guides a roller 9 with a central circumferential groove havinga width corresponding to the thickness of the flatiron 8. This roller ismounted on a bolt 10 the ends of which are connected to the free end ofa lever 11 having its front portion forked. The lower end of this lever11 is pivotally journalled on arms 12 which are fixedly connected to theflatiron 5. The pivot axis of lever 11 extends parallel to the axis ofthe hinge means 3.

Pivotally mounted on the bolt 10 and, more specifically, at both sidesof the roller 9 are two protrusions 13 of a traverse 14. The ends ofsaid traverse are engaged by tension springs 15 which are suspended inhooks 16 and which are located closely above the hinge means 3 on thebridge plate 1.

When the bridge occupies its rest position shown in the drawing, the twotension springs 15 are preloaded. In order that this position can bemaintained, the protrusions 17 of the lever 11 catch behind a transversemember 18 of the flatiron 8. However, if desired, the rest position ofthe bridge may also be secured by other detachable arresting means.

If the bridge plate 1 is to be pivoted downwardly into its position ofaction, the bridge plate must be prevented from shock-like impacting. Tothis end, the

bridge plate 1 rests during the pivoting movement in downward directionon the roller 9 or the free end of the lever 11 which in its turn can bepivoted downwardly only while tensioning the tension springs 15. Duringthe pivoting movement of the bridge plate 1, the roller 9 moves on thecam 7 forwardly in the direction toward the front end 6 of the bridge.If desired, the traverse 14 may be caught by an elastic abutment 19.

After the bridge has been used, the bridge plate 1 is manually pivotedupwardly. This is possible without any difficulties, i.e., while onlyusing small forces, because the tension springs 15 will be preloadedwhen the bridge plate is lowered. Due to the above mentioned leverarrangement in cooperation with the springs 15 and due to theillustrated S-shaped configuration of the path of cam 7, the goal willbe realized that when pivoting the bridge upwardly, the necessary forcewill be uniform over the entire pivot range. The two springs 15 are sodimensioned that the required force will be low.

Experience has shown that the S-shaped path of cam 7 will beparticularly favorable when this path in the first portion(approximately the first half) is concave and in the second or lastportion is convex. Such an arrangement will with the changing leverangle and the respective angle of attack of the tension springs 15 leadto the desired effect. The lever length corresponds in this connectionapproximately to half the length of the bridge plate, and the tensionsprings 15 will in the rest position of the bridge define together withthe then vertical lever 11 an angle of approximately from 12 to 18.Moreover, in the rest position of the bridge, the distance of the lever11 from the bridge plate corresponds to approximately the distance a(hinge means lower pivot area).

It is, of course, to be understood that the present invention is, by nomeans, limited to the specific showing in the drawing but also comprisesany modifications within the scope of the appended claims.

What I claim is:

1. In combination with a ramp, a bridge structure pivotally connected tosaid ramp for transferring a load over said bridge structure onto andfrom said ramp, said bridge structure including: a bridge plate. hingemeans hingedly connecting one end portion of said bridge plate to saidramp for selectively pivoting said bridge plate about the axis of saidhinge means from a substantially vertical rest position to an at leastapproximately horizontal position of use and vice versa, tension levermeans pivotally supported by said ramp for pivoting about an axissubstantially parallel to the axis of said hinge means and located inspaced relationship thereto, spring means having one end thereofanchored within the region of said axis of said hinge means and havingthe other end anchored within the region of the free end of said levermeans, and cam means connected to said bridge plate and having a camsurface support ing said free end of said lever means, said spring meanscontinuously urging said free end of said lever means toward said camsurface and having its shortest extension when said bridge plateoccupies its substantially vertical rest position, that end of saidtension spring means which is within the region of the axis of saidhinge means being connected to said bridge plate, the length of saidlever means approximately being equal to half the length of said bridgeplate, said lever means in its substantially vertical rest positionbeing spaced from said bridge plate by a distance approximatelyequalling the distance between the horizontal plane through the axis ofsaid hinge means and the pivot axis of said lever means, said camsurface having an S- shaped contour and that portion of said cam surfacewhich in the substantially vertical rest position of said bridge plateis closest to said roller means being concave whereas the other portionof said cam surface has a convex surface, said concave and said convexportions of said cam surface merging with each other at about thecentral region of said cam surface, and in said substantially verticalrest position of said bridge plate said roller means engaging andexerting pressure upon said convex portion of said cam surface.

2. A bridge structure in combination according to claim 1, whichincludes shaft means supported by said free end of said lever means,roller means supported by said shaft means and engaging said camsurface. and holding means pivotally supported by said shaft means andhaving that end of said spring means connected thereto which is anchoredwithin the region of said free end of said lever means.

3. A bridge structure in combination according to claim 1, in which saidfree end of said lever means is fork-shaped and carries said shaftmeans, and in which said holding means includes a traverse having oneend of said spring means connected thereto and also having extensionmeans respectively located on opposite sides of said roller means whilepivotally resting on said shaft means.

4. A bridge structure in combination according to claim 1, in which theplane of symmetry of said lever means coincides at least approximatelywith the longitudinal plane of symmetry of said bridge plate, and inwhich said lever means is arranged on that side of said bridge platewhich when the latter is in its position of use represents the bottomside.

5. A bridge structure in combination according to claim 1, in which inthe substantially vertical rest position of said bridge plate saidtension spring means defines with said lever means an angle ofapproximately from 12 to 18.

1. In combination with a ramp, a bridge structure pivotally connected tosaid ramp for transferring a load over said bridge structure onto andfrom said ramp, said bridge structure including: a bridge plate, hingemeans hingedly connecting one end portion of said bridge plate to saidramp for selectively pivoting said bridge plate about the axis of saidhinge means from a substantially vertical rest position to an at leastapproximately horizontal position of use and vice versa, tension levermeans pivotally supported by said ramp for pivoting about an axissubstantially parallel to the axis of said hinge means and located inspaced relationship thereto, spring means having one end thereofanchored within the region of said axis of said hinge means and havingthe other end anchored within the region of the free end of said levermeans, and cam means connected to said bridge plate and having a camsurface supporting said free end of said lever means, said spring meanscontinuously urging said free end of said lever means toward said camsurface and having its shortest extension when said bridge plateoccupies its substantially vertical rest position, that end of saidtension spring means which is within the region of the axis of saidhinge means being connected to said bridge plate, the length of saidlever means approximately being equal to half the length of said bridgeplate, said lever means in its substantially vertical rest positionbeing spaced from said bridge plate by a distance approximatelyequalling the distance between the horizontal plane through the axis ofsaid hinge means and the pivot axis of said lever means, said camsurface having an S-shaped contour and that portion of said cam surfacewhich in the substantially vertical rest position of said bridge plateis closest to said roller means being concave whereas the other portionof said cam surface has a convex surface, said concave and said convexportions of said cam surface merging with each other at about thecentral region of said cam surface, and in said substantially verticalrest position of said bridge plate said roller means engaging andexerting pressure upon said convex portion of said cam surface.
 2. Abridge structure in combination according to claim 1, which includesshaft means supported by said free end of said lever means, roller meanssupported by said shaft means and engaging said cam surface, and holdingmeans pivotally supported by said shaft means and having that end ofsaid spring means connected thereto which is anchored within the regionof said free end of said lever means.
 3. A bridge structure incombination according to claim 1, in which said free end of said levermeans is fork-shaped and carries said shaft means, and in which saidholding means includes a traverse having one end of said spring meansconnected thereto and also having extension means respectively locatedon opposite sides of said roller means while pivotally resting on saidshaft means.
 4. A bridge structure in combination according to claim 1,in which the plane of symmetry of said lever means coincides at leastapproximately with the longitudinal plane of symmetry of said bridgeplate, and in which said lever means is arranged on that side of saidbridge plate which when the latter is in its position of use representsthe bottom side.
 5. A bridge structure in combination according to claim1, in which in the substantially vertical rest position of said bridgeplate said tension spring means defines with said lever means an angleof approximately from 12* to 18*.